A majority bonus system (MBS, also called a minority-friendly majoritarian system) is a mixed-member, partly-proportional electoral system that gives extra seats in a legislature to the party with a plurality or majority of seats. Typically, this is done with the aim of providing government stability, particularly in parliamentary systems.
The size of the majority bonus can vary substantially, is usually a fixed number of seats, and may be conditional on the number of votes for each party. However, a relatively small majority bonus (such as in the reinforced proportionality system of Greece) may not always guarantee that a single party can form a government. At the same time, as the majority bonus is allocated in a non-compensatory manner, if the majority bonus is as high as 50%, and the largest party which has 50% of the popular vote receives it, this party may win as many as 75% of all seats available. This differentiates it from the similar majority jackpot system.
